1. Field of the Invention
The present invention relates to a biaxially oriented laminated film, and more particularly to a biaxially oriented laminated film suitable for the base film of a magnetic recording media, which gives a high quality image when it is used as the base film of the magnetic recording media and which has an excellent abrasion resistance.
2. Description of the Prior Art
A biaxially oriented polyester film containing practically spherical particles of colloidal silica is known and described in, for example, JP-A-SHO 59-171623. A biaxially oriented laminated polyester film which has an outermost layer containing inorganic particles and which is suitable for a base film of a magnetic recording media is also disclosed in, for example, JP-A-HEI 3-1941.
In such conventional biaxially oriented films, however, there is a problem that the surface of the film having fine protrusions is liable to be abraded by rolls and guide pieces used in, for example, magnetic solution coating process, calendering process, winding process or cassette built-in process, when the film is used as the base film of a magnetic recording media and processed into the magnetic recording media. Recently, since the speeds of the above processes increase, the problem becomes remarkable.
Further, recently, the dubbing speed of a magnetic recording media has been increased by, for example, the development of high-speed magnetic field transfer technology. With the conventional biaxially oriented films described above, when the film is used as the base film of a magnetic recording media and the image recorded in the magnetic recording media is dubbed, the signal/noise ratio (S/N) is large and it is difficult to obtain a high-quality image, particularly when the dubbing is carried out at a high speed.